Mechanically-driven vehicle accessories have traditionally been belt driven or gear driven from the engine. These accessories include air compressors (for pneumatic devices), air conditioning, power steering pumps, engine coolant pumps, fans, etc. Often, these accessories are designed to operate at lower engine speeds, such as at an engine idle condition. As a result, when the engine operates at higher speeds, the accessories may operate at inefficient operating bands. Furthermore, mechanically-driven vehicle accessories are usually unable to be powered while the engine is off. This may cause high priority accessories to be unable to perform necessary functions after a vehicle has been driven and the engine has been turned off (such as a water pump used to cool the engine).